Gas analyzers are used to measure gases exhaled by a patient. In particular, carbon dioxide is monitored to determine the physiology of a patient. This is of prime importance during and immediately after surgery, and during respiration therapy. A major problem area in the analysis is the removal of entrained liquid either from the patient or the condensation from the breadth or humidified oxygen supplied by a ventilator. This problem is further complicated by the need for rapid pneumatic response time, so that the visual waveform of the patient's exhaled CO.sub.2 displayed electronically on a breath-by-breath basis will be faithfully reproduced. Any large and/or dead volumes anywhere in the sample train can cause mixing of the gas and tend to integrate rapid peaks and ultimately degrade the waveform.
Filters have heretofore been used in breath sampling lines, such as hydrophobic membranes (U.S. Pat. No. 4,558,708), sintered metal (U.S. Pat. No. 4,558,709) and water absorbents (U.S. Pat. No. 4,446,869). Such filters, however, become saturated and must be changed over extended sampling periods. Mechanical liquid traps in which liquid is collected in a reservoir have greater liquid capacity, see, for example, U.S. Pat. No. 4,579,568, but the increased volume of the system increases response time and convection or diffusion of the gas from the liquid reservoir dilutes the breath sample.